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Constant clicking problem (ipod 5g)

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saratoga:

--- Quote from: PinkZeppelin on March 31, 2006, 06:08:01 PM ---
Because of the sound noise problems I have found in both flavors of rockbox (both on my H140 and the Ipod 5G), and the fact that even some people (including at least 1 rockbox developer) seemed to think the X5 sounded fine when it was playing back with a 10khz lowpass filter make me a bit skeptical about rockbox audio quality claims...


--- End quote ---

Many people cannot hear high frequencies well or at all, and do not use good headphones.  Amoung those that can hear them, sensitivity to them is generally very low.  This is one of the principles used in MP3 encodeing. 

Its really not surprising that many people didn't notice the sample rate problem.

PinkZeppelin:

--- Quote from: saratoga on March 31, 2006, 06:13:33 PM ---This is one of the principles used in MP3 encodeing. 

Its really not surprising that many people didn't notice the sample rate problem.

--- End quote ---

Mp3 encoding is supposed to have a lowpass around 18khz, not 10khz.  Either people listen to music at ridiculously low bitrates, or have no clue on how to properly encode mp3s. 

lostlogic:
The only claim I know of that rockbox makes about audio quality is that unlike many stock firmwares, we do not futz with the audio output of the codec, we simply play it back to the hardware as is (unless you turn on the various 'enhancement' options available).

As for the H140 buzz, that occurs with stock and rockbox firmwares as far as I know (at least it did on my H340), so don't try to pin that on rockbox, it's a problem with isolation on the iRiver players.

Finally, I do not doubt that the clicking problem occurs, as I said, we have a known issue with our I2C driver which could cause such a problem.  When using Rockbox, you need to realize that it is a _free software_ project.  It is developed for fun.  If you have a problem with it, fine, but don't act _entitled_ to a fix or  change to rockbox behavior.  You are more than welcome to develop your own solution, as the source is there for your modification.

I (unfortunately) do not have the software, hardware, nor knowledge to do RMAA analysis of my player, but I would be interested in other datapoints on the clicking issue.

Llorean:
Also, keep in mind that Rockbox has not been RELEASED yet. On ANY of the software codec targets. While it's at version 2.5 for the Archoses, the overall 3.0 will be version 1 for the iRivers, and 3.1 will be the first release for the iPods. Until then, you shouldn't *expect* anything to work a specific way, or even at all. So while bug reports are welcome, you are using a prerelease software, and should keep that in mind at all points in time.

saratoga:

--- Quote from: PinkZeppelin on March 31, 2006, 06:23:13 PM ---
--- Quote from: saratoga on March 31, 2006, 06:13:33 PM ---This is one of the principles used in MP3 encodeing. 

Its really not surprising that many people didn't notice the sample rate problem.

--- End quote ---

Mp3 encoding is supposed to have a lowpass around 18khz, not 10khz.  


--- End quote ---

Please don't misquote me.  What I said was:


--- Quote --- Amoung those that can hear them, sensitivity to them is generally very low.  This is one of the principles used in MP3 encodeing. 
--- End quote ---

Note that I said people had low sensitivity, not that they were lowpassing all high frequency sounds.  Theres a very big difference between the two. 

Anyway, MP3 lowpass is configurable, but the spec clearly intends you to use no higher then ~15-16KHz, not 18KHz.  Even if you force the lowpass higher, very little high frequency content is encoded (or rather very little bitrate is allocated due to the sfb21 issue in the MP3 format).  For this reason, when you FFT MP3 encoded audio, even with LAME, much of the energy above 16KHz is actually noise.


--- Quote ---Either people listen to music at ridiculously low bitrates, or have no clue on how to properly encode mp3s. 
--- End quote ---

Or, as I already suggested, they're insensitive to higher frequency sound.

You may be interested in looking at the equal loudness curves here:

http://en.wikipedia.org/wiki/Absolute_Threshold_of_Hearing

or the information here:

http://en.wikipedia.org/wiki/Psychoacoustics

Note that high frequency sensitivity drops off VERY quickly with age.  You're already well past your prime by the time you're 20.  By age 40, the average male has already lost 10 fold as much high frequency sensitivity as they've lost at low frequencies. 

Its perfectly reasonable that many people using Rockbox would never notice a 22Khz sample rate, even listening to lossless audio.

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